Wind turbine blade aerodynamics of the NREL phaseVI rotor near peak power

A Parallelized Coupled Solver (PCS) for the numerical analysis of wind turbines is applied to the NREL Phase VI rotor configuration near peak power under steady and no-yaw conditions. The PCS solver consists of a commercially available Navier-Stokes code, CFX V5.6, which is confined to the immediate vicinity of one rotor blade, and a Vortex-Panel method, which models the vortex sheet of a two-bladed rotor and accounts for the far-field. The Navier-Stokes solver assumes fully turbulent flow using the k-ω turbulence model. Numerical results obtained with the PCS solver show good agreement with experimental data from the NASA Ames wind tunnel. It is found that close to peak power a vortex tube due to spiral separation forms on the upper surface of the blade near the 40% radial station. This vortex tube is counter-rotating to the root vortex at the 25% radial station. It grows in strength and size for higher wind speed. It is shown that such strong 3D effects cannot be detected with an incompressible vortex line method (VLM) based on strip theory. The PCS solver, on the other hand, exhibits complex 3D physical phenomena occurring at peak power.